Generally, in a printing factory all kinds of printing products are manufactured by using water or oil ink, and therefore waste water containing waste ink is generated. Further, even lubricating oil may be contained in the waste water due to activation of printing machines.
Meanwhile, the generation of the waste water containing the oil is not excluded in a general factory which machines is worked.
To prevent pollution of environment due to discharge of waste water out of factory, there is provided a conventional device which filters or purifies waste ink or oil contained in the waste water by using a filtering method by means of a filter, a sewage purification method, or a sedimenting method with medicines.
However, in the conventional device using the filtering method with the filter, if the filter through which a variety of sludge such as a waste ink particles, oil particles and so on is filtered is waste without any treatment, the filtered waste water is restored to its original waste water in the case where water is admixed to the wasted filter. Therefore, there is an inconvenience in that the completely used filter should be destroyed by fire.
Also, in the conventional device using the sedimenting method with medicines there are problems in that a purification cost is increased due to expensive medicine usage and a sediment should be re-treated. Additionally, if the treated water with the medicines is directly discharged, there occurs a problem in that river contamination is naturally accompanied since the treated water is short of the biological oxygen demand (BOD).
Due to an illegal exhaust of factory waste water, the waste water flows to general sewage or rivers to deteriorate soil or the water quality, which results in a serious destruction of natural environment.